Some time ago, TTAC published a guest post on the topic of driving under the influence of cannabis that more or less discounted the dangers of puffing while puttering around, at least for experienced potheads. Needless to say that post provoked some heated discussion. Now that Colorado has legalized marijuana for general use, the legislature there has decided that it was necessary to officially define “too high to drive”. It’s not clear if the reason was traffic safety or revenue since instead of using a behavioral standard for impairment, the new law creates an arbitrary blood level of THC, the active ingredient in cannabis, that would define a driver as illegally impaired, whether or not they were measurably impaired in their driving. Critics of the way impaired driving is enforced already say that the drive to lower legal blood alcohol content limits was intended to catch people who weren’t actually impaired, driving safely but drunk according to the law, a classic case of malum prohibitum rather than malum in se. Setting an arbitrary limit for THC would allow DUID, driving under the influence of drugs, to join DUI as a cash cow for city, county and state governments.
The new law in Colorado allows juries to convict someone of DUID if blood tests show a THC level of at least 5 nanograms per milliliter of blood. That level is the same as enacted in Washington following that state’s marijuana legalization initiative. It’s not entirely clear why the five nanogram limit was chosen. While some novice pot smokers may actually be impaired enough to affect their driving with 5ng/mL of THC in their blood, Reason, the libertarian publication, reports that many drivers are perfectly competent at many times that level of cannabinoids in their system.
One reason for establishing some kind of limit, as opposed to zero tolerance, is that in Washington and Colorado marijuana is no longer illegal for regular use. If a drug is illegal, any use should put you in a jackpot if you’re nabbed driving with it in your system. If it’s legal to use marijuana, however, the state has no compelling interest to prosecute drivers who do have some level of THC in their systems but aren’t actually impaired. KIRO, the CBS television affiliate in Seattle, decided to test both medical marijuana users and recreational pot smokers to see just how much pot they could smoke before being impaired.
Addy Norton is a 27-year-old woman who smokes medical marijuana every day. When she arrived at the KIRO test, she was already legally impaired per Washington state law, 16 ng/mL, more than three times the legal limit. According to the professional driving instructor who rode along (with a foot over the dual control brakes), she completed the baseline test on a driving course satisfactorily, though way over the legal THC limit. Then they proceeded to get Addy really high. After smoking 3/10 of a gram (% THC wasn’t specified but medical marijuana is typically over 20% THC), she tested at 36.7 ng/mL. At over 7 times the legal limit her driving was still not impaired. Smoking another 6/10ths of a gram only put her at “borderline” impairment, according to a drug recognition expert from the Thurston County, Washington Sheriff’s Office. To find out how much 0.9 gm of medical marijuana is, I checked with one of my own experts on marijuana, let’s call him Sativa Bongstein. Bongstein said that while he never measured how many joints he gets out of an eighth of an ounce of medical marijuana, an eighth will keep him continuously high for most of his waking hours over two days. So yeah, smoking about a fourth of that, almost a gram of medical marijuana, in one sitting should get you pretty high, however, according to the tests, it may barely impair your driving. It was only after Norton smoked a total of 1.4 grams and reached a THC titer of 58.8 ng/mL, more than eleven times the legal 5 nanogram limit, that she clearly failed the driving test.
The test results were reproduced by KIRO with people who used marijuana less frequently than Addy but still drove without noticeable impairment at levels far above the 5 nanogram limit. KDVR, a Fox affiliate in Denver, performed similar tests with a medical marijuana user who arrived with a 21 nanogram THC level, though he hadn’t yet smoked anything that day. Not only did he pass his driving test on a simulator as stoned as he likely already was when he walked in the door, raising his level to 47 ng/mL did not impair his simulated driving either. A drug recognition expert from the Thurston County Sheriff’s Office said his driving was fine. “[He] is doing pretty well,” the police officer said as he watched the driver being tested at the higher THC level, more than 9 times the legal limit. “He’s being a safe driver. It’s doubtful that I would have pulled him over. He hasn’t shown any degree of impairment.”
While some people may indeed be impaired at 5 ng/mL, the tests show that obviously some people are not. There is some habituation and tolerance involved so regular pot smokers might learn to adapt and drive at a THC level that would impair novice users of marijuana.
THC is stored in fatty tissue so it can remain in the blood system of regular users long after the effects of the drug have worn off. Even someone who hasn’t smoked marijuana in years can test above 0.0 ng/mL and daily smokers may never fall below the 5 ng legal limit.
The Colorado General Assembly rejected the current standard five times, aware of the fact that it was an arbitrary standard and not a good indicator of impairment, but it finally passed the same week that the legislature passed a law regulating retail marijuana stores.
Though police still need “reasonable suspicion” to pull you over and request a blood test, that could mean seeing you with a hand rolled cigarette in your hand, not necessarily driving in an impaired manner. Once cited, the chances of being acquitted seem to be slim. While Colorado’s new law does not make people automatically guilty of driving under the influence of drugs if they are measured to be at or above the 5 ng limit, it still creates a presumption of impairment. Defendants can attempt to rebut the presumption, but Denver defense attorney Rob Corry, who specializes in DUID cases, says that in reality, with a “permissible inference” of impairment at 5 ng, of DUID if they test above that level. Instead it creates a presumption that defendants can try to rebut by presenting evidence that they were not in fact impaired. But Denver attorney Rob Corry, who frequently represents DUID defendants, thinks that opportunity will not make much difference in practice. With a “permissible inference” of DUID at five nanograms, he says, “A person coming into court is guilty until proven innocent. If you put a number on it, juries are going to latch onto that five-nanogram number, whether it’s a permissible inference or a per se [standard], and the effect will be that innocent people are convicted.”
Ronnie Schreiber edits Cars In Depth, a realistic perspective on cars & car culture and the original 3D car site. If you found this post worthwhile, you can get a parallax view at Cars In Depth. If the 3D thing freaks you out, don’t worry, all the photo and video players in use at the site have mono options. Thanks for reading – RJS